Joined: Fri May 16, 2008 1:05 amPosts: 2437Location: Sold my soul to Satchboy for an avatar

I have a multi-speed dremel with a flexi shaft. I have used it on Plexi before with success. My only experience with Acrylic is with a drill and jigsaw. I found that acrylic melts very quickly from tool heat. I've been able to work with the jigsaw, because it's an adjustable speed model, and by spaying the blade/sheet with water. However, for this project, a jigsaw isn't going to work in a lot of places.

Anyone have much experience with the Dremel on acrylic? Which bits work well? Should I just stick with hand tools and skip the power?

I have always used a Dremel to cut plastics with. Just have to go slow so you aren't just melting stuff.

Same here. Start at the lowest speed setting and be patient, you can gradually increase the speed if needed. The regular reinforced cutting wheels should do the job for you. I have also seen people use jigsaws and bandsaw to cut cast acrylic, but I can't speak from personal experience.

I just found a handy little trick for cutting all kinds of plastic using any kind of rotary cutter....(regular dish washing liquid mixed with water). If you have somebody spray it as the gutter is working, it cools the plastic and prevents fracturing. It also micro-polishes the cut surface.

I just found a handy little trick for cutting all kinds of plastic using any kind of rotary cutter....(regular dish washing liquid mixed with water). If you have somebody spray it as the gutter is working, it cools the plastic and prevents fracturing. It also micro-polishes the cut surface.

I would have to agree with Saabjock the soap acts as a lubricant to decrease friction and also cuts the surface tension of the water to decrease heat you can also use bar soap on drill bits by dragging the bit over the soap so that soap gets scrapped into the bit.

Joined: Fri May 16, 2008 1:05 amPosts: 2437Location: Sold my soul to Satchboy for an avatar

in my experience, cutoff wheels are a bad idea in general for cutting plastics. While they're called "cut"off, they're actually grinding tools. true cutting tools, ie, those with teeth tend to be better on plastic. The wheels are awesome on metal, because you grind away the metals. Due to metals hardness, the tools with teeth tend to dull to quick, which is why the grinders work better there. However, grinding happens by lots of friction on the surface. With plastics, that friction turns into melting heat. Look at the glowing red you get when cutting metal, vs. cutting it with a jigsaw. Using a lubricant on a grinder is counterproductive to the way that they work.

The soap recommendations do sound good for the cutting bits/blades, though. It should work similar to the cutting oil used on metal cutting tools.

In my attempts to find good cutting tools, I discovered that commercial shops use water cooled routers with single edged bits and water cooled bandsaws. I read somewhere that fewer teeth is better for creating less heat (makes sense to me), which seems substantiated by their use of single edge router bits.

I have found that toothed cutters work the best, and for lubrication, while soap works, the best thing I have found is ATF, just the cheapo stuff, coat the bits in it. If you are using bur bits on aluminum, the ATF will also prevent clogging of burs.

Variable speed scroll saws are fine and probably the best choice, but not every part you want to cut are so easy to get on the bench. Hand-held Jigsaws are a good option but can also be a mess working with on many pieces we actually want to cut. Say it's the front bezel and we select a jigsaw, then we need space underneath to clear the blade or it'll bounce off the bench. You'd also want a thin blade (tooth to back, not width) to make turns. These are hard to find in the tooth count desired for plastic and will usually require modifying a standard sized blade. Great if you want a square, bad for small circles and corners.

Grinders are fine for plastic and have used a Dremel drums and discs for this work since...I guess ever (not just computers). It just takes some common sense on how fast to go, how deep of a bite to take with it, and when to pause if it starts to feel like it's melting. I'll even use a hole saw or a bench grinder with much success. We just have to realize that these tools are mostly used for wood and metal and adapt. Great for plexy too! Once you get your cut final, just take a butane/MAP torch to the edges for that glassy look.

I wouldn't load up a thin composite cutting disc with soap or water (or any liquid for that matter). It may be fine if you keep it at 3K rpm or below, but get that thing above that at any time and it can fracture and separate. In normal plastic cutting, you may feel it bog down a bit and adjust the speed to make up for it. Pull it out and it spins back up...fast. I've blown a lot of discs up and it doesn't hurt so bad on the hands, but am lucky I wear safety glasses pretty much all the time in the garage. Applying liquid while spinning is the best practice as it will not collect on the disk (centrifugal force tosses it off and onto the work surface) and to use just enough to get you through the cut itself. This is why the "3rd hand" was recommended by others to apply while working, not between.

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